Quantitative analysis of elastic moduli and structure of B 2O 3–SiO 2 and Na 2O–B 2O 3–SiO 2 glasses

Abstract

The average cross-link density n ̄ c , number of network bonds per unit volume n b, average stretching force constant F ̄ and atomic ring size ℓ have been calculated for the binary B 2O 3–SiO 2 and ternary Na 2O–B 2O 3–SiO 2 glass systems. These data have been used to calculate the bond compression bulk modulus K bc and Poisson's ratio σ cal for each glass sample. The variation of these parameters and the ratio K bc/ K e with composition were discussed quantitatively in terms of the change in structure of the glass network. The result showed that the connectivity and hence the rigidity of the B 2O 3–SiO 2 glasses decreases with increasing B 2O 3 concentration. Whereas increasing of Na 2O modifier in Na 2O–B 2O 3–SiO 2 glasses increase the cross-link density due to the transformation of three-fold-coordinated boron atoms into four-fold-coordinated ones. This in turn raises the resistance of the network to deformation and increases the observed density and elastic moduli of this glass system. Moreover, the theoretical elastic moduli have been obtained for each glass sample and compared with the corresponding experimental values. The results showed excellent agreement for the majority of the samples examined.